A large share of surface water resources in Sahelian countries originates from Guinea’s Fouta Djallon highlands, earning the area the name of “the water tower of West Africa”. This paper aims to investigate the recent dynamics of the Fouta Djallon’s hydrological functioning. The evolution of the runoff and depletion coefficients are analyzed as well as their correlations with the rainfall and vegetation cover. The latter is described at three different space scales and with different methods. Twenty-five years after the end of the 1968–1993 major drought, annual discharges continue to slowly increase, nearly reaching a long-term average, as natural reservoirs which emptied to sustain streamflows during the drought have been replenishing since the 1990s, explaining the slow increase in discharges. However, another important trend has been detected since the beginning of the drought, i.e., the increase in the depletion coefficient of most of the Fouta Djallon upper basins, as a consequence of the reduction in the soil water-holding capacity. After confirming the pertinence and significance of this increase and subsequent decrease in the depletion coefficient, this paper identifies the factors possibly linked with the basins’ storage capacity trends. The densely populated areas of the summit plateau are also shown to be the ones where vegetation cover is not threatened and where ecological intensification of rural activities is ancient.

中文翻译：

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Fouta Djallon 高地仍然是西非的水塔吗？

萨赫勒国家的很大一部分地表水资源来自几内亚的富塔贾隆高地，因此该地区被称为“西非水塔”。本文旨在调查 Fouta Djallon 水文功能的近期动态。分析了径流和耗竭系数的演变以及它们与降雨和植被覆盖的相关性。后者在三个不同的空间尺度和不同的方法中被描述。1968-1993 年大旱结束 25 年后，年排放量继续缓慢增加，几乎达到长期平均水平，因为自 1990 年代以来，在干旱期间排空以维持河流流量的天然水库一直在补充，这解释了排放量缓慢增加。然而，干旱开始以来的另一个重要趋势是，Fouta Djallon 上游盆地的大部分枯竭系数增加，这是土壤持水能力下降的结果。在确认了这种增加和随后减少的消耗系数的相关性和显着性后，本文确定了可能与盆地存储容量趋势相关的因素。山顶高原人口稠密的地区也被证明是植被覆盖不受威胁和农村活动生态集约化历史悠久的地区。在确认了这种增加和随后减少的消耗系数的相关性和显着性后，本文确定了可能与盆地存储容量趋势相关的因素。山顶高原人口稠密的地区也被证明是植被覆盖不受威胁和农村活动生态集约化历史悠久的地区。在确认了这种增加和随后减少的消耗系数的相关性和显着性后，本文确定了可能与盆地存储容量趋势相关的因素。山顶高原人口稠密的地区也被证明是植被覆盖不受威胁和农村活动生态集约化历史悠久的地区。